


The Concupiscence Conjectures

by Turdle



Series: The Soldier's Element [1]
Category: Fullmetal Alchemist
Genre: Alternate Universe - Canon, Awkwardness, Canon - Manga, Cunnilingus, Enthusiastic Consent, F/M, First Time, For Science!, Kissing, Oral Sex, Pre-Canon, Romance, Teen Romance, Teenagers
Language: English
Status: Completed
Published: 2012-11-30
Updated: 2012-12-31
Packaged: 2017-11-19 21:35:55
Rating: Mature
Warnings: No Archive Warnings Apply
Chapters: 6
Words: 13,562
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/577897
Author URL: https://archiveofourown.org/users/Turdle/pseuds/Turdle
Summary: <blockquote class="userstuff">
              <p>The Concupiscence Conjectures (Or, Roy Mustang and Riza Hawkeye's very scientific theorem on making out.)</p><p>With hypotheses to be proven, and a summer to spare, Riza and Roy steal moments to themselves between their studies to work on their bonds.</p>
            </blockquote>





	1. Chapter 1

**Author's Note:**

> June, 1903. Ashford, Eastern Amestris.

Kissing Roy Mustang had turned out to be a very good idea. 

At some point she had scooted onto his bed, and they'd put aside the books he was supposed to be studying in favor of more adventurous pursuits. It wasn’t the first time they’d snuck a small exchange of kisses between his study breaks, but before they’d mostly been cut short. But this time, Riza had prolonged it a little longer, brushing her lips against the corner of his mouth before he adjusted to deepen their kiss. Leaning against his headboard, she had twined her arms around his neck and drawn her legs up to her chest, continuing their kiss eagerly. 

Everything seemed to be working quite nicely, and though she wasn’t quite sure about his tongue’s placement, the way his hands slid over her waist was nice enough to merit a pleased hum from the back of her throat. Maybe kissing with tongues was just something she’d get used to. Roy seemed like he might know about these sorts of things, and while they’d tried it once or twice before, it had always ended after she pointed out he should probably get back to studying. 

This time, Riza didn’t feel particularly eager to get him to refocus on what he was supposed to be doing. So when Roy interrupted their kiss first, she was rather surprised. She opened amber eyes with a quizzical look, peering back at him as he leaned back on his knees on the bed, eyeing her up and down thoughtfully.

“You seem a little tense.” Roy said, not appearing upset, but she could still hear the concern in his voice. It was a question, more than anything. Riza looked back at him, and shook her head firmly. 

“I’m fine.” she answered, brushing back her bangs behind her ears. 

“You’re sort of curled up in a little ball, and your shoulders are tensed up.” Roy pointed out, and Riza self-consciously dropped her shoulders. She hadn’t been thinking about it while she was doing it. Roy didn’t say anything else, but it was clear by the look in his sharp eyes that he was expecting some sort of communication. 

Riza sighed. “Have you ever done this before?” 

Roy blinked, as if taken aback by the question, and then swallowed. “Um, which part?”

“This kind of kissing, and the…other stuff.” Riza said, suddenly feeling awkward for having brought it up. It really wasn’t her business, and she’d never particularly worried or even cared about any other girls he might have had kissed, but it still seemed obvious that at almost eighteen, maybe Roy knew a little something she didn’t. Her wealth of experiences was mostly limited to him. “I haven’t done this with anyone else.” she clarified a little lamely. 

This seemed to cause Roy’s eyes to widen slightly. At least now he got what she was getting at. His hand went up to rub the back of his neck like he did whenever he felt awkward, or embarrassed, and Riza bit her lip to keep from smiling. It was rather endearing to watch him whenever he did that. 

“It’s—I mean it’s not something I’ve done a whole _lot_ of. I was busy. Studying.” Like he should have been doing right now. Roy raised a brow, giving her that silly half-smirk he always gave when he was being too confident about something. “It can’t be too different from a scientific experiment, can it?” Roy asked, clearing his throat. “If the results aren’t satisfactory, change the parameters of the experiment.”

“And if the experiment fails?” Riza asked pointedly. 

Roy shrugged. “No such thing as a failure. Just a new set of data to work off of. If you don’t like anything, we can stop.” he assured, leaning back towards her with a smile. Riza grinned in kind, rolling her shoulders as leaned back to press her spine back into his headboard. 

“Do you have a hypothesis to work off of, Mister Mustang?” She said with a cheeky grin of her own. 

“Sort of.” Roy said quietly, his eyes dropping as he chewed his lip and gazed at the spot where her skirts rode up over her knees. They were still drawn up against her chest, and Roy kneeled before her causing Riza’s face to flush in realization that he did have a plan of some sort. And before she could worry about what that was, Roy gave her another half-smile that made his eyes seem too black, and that gave her a funny - but pleasant - turn in her stomach. 

“Do you mind if I kiss your knees?” He said softly, and Riza snapped her chin up, giving him a look. 

“My knees?”  Riza said in surprise. She moved to grab his bedsheets, fisting her hands into his blanket before she gave him another confused look. It seemed like such an odd request, but Roy seemed to think it was perfectly normal. (But then, he’d just admitted he didn’t have half the idea she thought he did.)

“Like this,” Roy motioned, sliding a hand under her calf, running his hand up until he hit the crook of her knee, and kissed the top of the spot where her skirt hem hit her legs. Riza gasped in surprise,  _that was nice_ , and let him slide her leg out; relaxing her sitting position. Roy’s lips slid down to her calf, working down to kiss her ankles in a light sort of way that caused her to squirm in her seat before he switched legs, and worked his way back up to her skirts. 

She didn’t realize she had been holding her breath as he lingered at her knees until Roy looked up again. “Alright?” Roy asked pleasantly. 

Riza nodded. “Satisfactory.” she said, trying to collect herself as calmly as she could. Roy smiled proudly before he moved again, reaching for one of her hands knotted in his bed sheet, and fitting his hand over hers. She laced their fingers together in response, slipping her palm against his. He brought her knuckles to his lips, and kissed them gently before he moved to position himself so that her legs were on either side of him. Roy held back a small distance, as if testing her new boundaries, and Riza leaned up, resuming her placement of a hand around his neck. 

 Leaning forwards, Roy moved her leg again, hooking his hand under her knee as he began to kiss her again. Admittedly, Riza thought, the access was a bit nicer now that she wasn’t blocking the broadness of his chest with her legs tucked up nearly to her chin. It certainly made the kissing more enjoyable, and Riza was quite certain her shoulders were no longer hunched up. Roy’s tongue swiped along the bottom of her lip, causing her mouth to tingle, and Riza wriggled to pull him closer to her. 

This seemed to cause a positive reaction in Roy, and he made a deep rumble in his throat that was encouraging. Riza’s tongue darted out, and she repeated the same thing he had done just moments ago, before running her tongue over the roof of his mouth. He leaned into her a little more heavily, and Riza reminded herself that smiling smugly while kissing would probably not be very beneficial. Instead, she hooked one of her legs over his encouraging the new level of comfort. This was starting to get easier as it went along. 

At some point between her moving, and his kissing, Roy’s hands had moved from her waist to the tie under her peter pan collar, fumbling with the knotting for a few moments before it started to unravel in his fingers. Breaking their kiss, Riza looked up and rose a brow. Roy’s fingers hovered where they were, the crisp blue ribbon in his hands. He flushed under her scrutinization, before awkwardly placing the ribbon on the bed beside her hips. Riza bit her lip for a moment, stifling a giggle. 

“Uh…” Roy explained. 

Riza wanted to look back down at her knees, but found herself looking at the buckle on Roy’s belt, sliver and glistening against his black slacks. Somehow, that didn’t seem to help her blushing a brilliant shade of pink. After a moment’s silence, Riza cleared her throat, and slipped her fingers over the top button at her collar. Roy blinked, watching her with fascination. “My shirt, right?” she said, popping the buttons free from their holes.

“If that’s alright.” Roy said, the apple of his throat bobbing slightly as he swallowed nervously. Riza sucked in a breath, popping her bottom lip back into her mouth before she nodded distinctly. It seemed fine, at any rate, and Roy’s hands were so nice on her waist that she thought his hands going elsewhere would probably be nicer. She stopped three buttons down, not quite sure what else to do before Roy leaned back in, his black hair tickling the underside of her chin as he kissed her exposed collarbone hesitantly. 

 _Scientific method_. Testing his theory was simply a part of that. Roy’s fingers looped the other buttons out of their holes, exposing the top of her chest and then the smooth lines of her belly that moved as she breathed in. Riza ran her palm up to the base of his skull and threaded her fingers through his hair gently, as Roy pushed her shirt out of his way. He didn’t seem too keen on rushing things, and Riza wondered if it was because he was getting a feel for what he was doing, or if it was because he was being gentlemanly about things. It was hard to tell, and her concentration slipped as he open mouth kissed the top of her breast where her bra ended and the strap began. Riza shifted again, her leg hitching closer to his hips, before she realized exactly how frustrating it was to feel his belt buckle dig into her. Still, she didn’t bother to reach for his pants quite yet, thoroughly enjoying the concentration Roy was putting into her chest. It wasn’t terribly graceful, but he blew gently over her when he removed his lips, and she shivered, goosebumps prickling her skin. 

Then he pulled down the straps of her bra, pulling them down over her shoulders to follow her blouse, not really bothering to unhook the offending garment. Riza’s grip on his hair tightened, and whatever words Roy had planned to say seemed to end up as some sort of throaty purring noise instead. Then he tested another kiss on the base of her throat as he palmed her right breast gently. 

“Oh.” Fingers curling in his hair, Riza tilted back her head as she sighed. “Can you um,” She said shakily, licking her lips. “-Just move your hand a little.” she directed firmly, noting that she was right about his hands. They were long and slender, and calloused in a few places from what she wasn’t sure - but it really felt very nice, and she didn’t want him to stop. 

“Like this?” Roy asked, brushing his thumb over her nipple curiously as he tried to move just enough to catch her expression. 

Stifling a squeak, she nodded, before adding somewhat shortly, “A little more.” 

Fortunately, Roy Mustang was an excellent student. Prodigies were often cocky, natural talent having gone to their head. But fully understanding that Roy was too damned stubborn to just give up when he wasn’t perfectly hitting the mark, Riza waited for him to roll her nipple between his fingers, letting him kiss her skin and return that funny burning feeling that nestled low in her body —

— _right about where that damn belt buckle kept digging in to her lower belly._

“ _Unm_ ,” Riza gasped, as Roy gently laved his tongue over her other nipple, before moving away to seal his lips over her flesh. “Roy,” she said carefully, before peeling his head back off her chest. There was a sudden flush of disappointment on his face, before Riza shook her head. “Roy, your belt. It’s digging into me.” She said slowly. “Could you take that off? The latch sort of sticks out, and it’s really starting to hurt the longer you lean on me like that.” 

“Oh, _uh_ \- Riza I don’t…I don’t think that’s the latch.” Roy stumbled, blinking a few times rapidly before he leaned back a little to reach for his belt. Stunned, he fumbled with it for a few long moments before finally getting the metal to unhook. 

“It was the belt that was bothering me.” Riza said quietly, as she clarified. She dipped her head down, before she remembered she was finding herself nearly face to face with the waistband of his pants. Hooking a finger through his belt loop, she averted her eyes from Roy’s crotch and slowly took in the rest of him. 

It was no big secret that now she hardly had much composure to speak of; what with her shirt and bra half off and her skirts rucked up from how he’d been leaning into her. But looking at Roy made it hard not to laugh, because if she was in a state of sorts, he seemed to be much worse off. And his pants did look distinctly tighter than they had been before, and Riza sort of pitied the lack of help removing the belt had done for him. Eventually, she realized, they would probably have to do something about that. 

A wry smile crossing her lips, Riza leaned forwards to whisper into his ear. “So, Mister Alchemist, whatever happened to equivalent exchange?” 

“What?” he asked dumbly. 

“Your shirt. You should probably take it off.” Riza said pointedly, moving her hands to the bottom of his shirt. She freed his buttons to expose him at his waistband and then his stomach, flat and beginning to be defined from exercise. At first she had thought his jogging at obscene hours of the morning and his insistence on pushups while he read alchemy texts were a bit ridiculous, but now she had to admit it was rather nice to admire the results. 

Roy moved to help her with the top buttons of his shirt, loosening the collar before he pulled the whole thing half undone over his head and discarded it by tossing the shirt onto the floor. “Better?”

“Much.” she declared with an impish smile. “Where were we…?” 

Roy rolled his shoulders, tilting his chin towards her chest, before trying delicately to place himself back where he had been resting before, appearing somewhat awkward as he tried to manage his growing erection. A blonde brow raised up as Riza moved to unhook her bra entirely and toss it onto the floor as well beside Roy’s shirt. As Roy sunk further into his mattress with a groan, he propped himself up, and Riza fought to keep from making another smart comment about his predicament. 

In typical Mustang generosity - under all that bravado - he sunk his chin into the spot between her breasts and looked up at her with an expression that made her stomach do another turn. It was affectionate, in a way Riza didn’t quite expect, but devious in another that made all too much sense.

They shifted again, Roy’s arm bracing on the other side while Riza opened her mouth to say something about the state of his expression. But instead of words, a loud clatter startled them both, and Riza looked around the room in search of its source. 

“What was…?” She asked sharply, ears straining to catch another noise, a shift of her father’s chair or the clicking noise his study door made when he finally bothered to unlock it and haunt the places of the house outside of that room. 

“I don’t-“ Roy stumbled carefully before he leaned over the side of his bed. “Oh. That.”

She closed her eyes in frustration as she realized he’d knocked his alchemy books to the floor. “My father might’ve heard that.” She warned, snatching her blouse from the floor, buttoning it half way before the tucked the ends of her shirt into her skirt’s waistband. Adjusting her collar, she gave a frustrated sigh as she realized there was nothing to be done about the fact that she was probably a shade of bright pink, and her hair was mussed, and worst of all, her clothes were rumpled and you could probably smell Roy’s aftershave all over her. Her father would just have to take one look at them both to decide to serve up apprentice en flambé for dinner. 

Which would be rather unfortunate. 

Pouting, Roy watched her scramble to leave. Normally he tried to wheedle her into staying another minute more. This time, however, it was a little different. He stood up before her, and she leaned up on slight tiptoes to kiss his cheek and then his mouth quickly in gratitude. “That was nice. Thank you. But…”

“You should get going before your dad wonders why books are falling from shelves.” Roy filled in helpfully with a mournful look.

“Exactly. Until you have another long study break…” Riza said, before opening his door, and ducking out of his room quickly. Her skirts flared around the edge of his door before she shut it behind her with a quick click. 

“ _Wait_ ,” Roy said a moment later, as he looked down to the ribbon in his hands. “-you forgot your tie.” Realizing she hadn’t heard him, Roy shrugged, and pocketed it. He’d give it back next time, when she noticed it was missing.


	2. Chapter 2

**Notes for the Chapter:**

> June, 1903. Ashford, Eastern Amestris.

Next time happened to be two days later, when Berthold Hawkeye had left two teenagers alone to speak with the local general store owner about the lack of a sufficiently brilliant pharmacist - or at the very least, a moderately adept apothecary - in town. Roy had occasionally gone on these trips with Master Hawkeye, buying chemicals here and there, and trying to mediate his Master’s scowling and the General Store owner’s growling about how ungrateful the ‘old bat’ was. 

However, on this occasion, Roy had distinctly not been invited, so he had retreated to the Hawkeye’s private sitting room, laying himself out across the worn plush chaise lounge. Unwieldy alchemy tome and notebook in hand, he’d set to work on what he considered to be an excellent use of his time. 

He started by twining a thin black bow over his fingers as he loosely dropped the end over the side of the couch. Then he waited.

“That’s not yours, you know.” Riza said firmly, when she finally slipped into the room, closing the door behind her. “You should give it back.” She set down a tray of shortbread cookies and tea on the end table by his head, and then held her hand out, motioning for him to hand her the ribbon. Roy pulled it just out of her immediate reach, a sure smile crossing his features. 

“Are you sure it’s not mine? I found it in my room earlier, and it certainly looks like it could be mine…how do you know my Aunt didn’t send it to me?” He teased lightly, glancing up at her with light dancing in his eyes. 

“I didn’t know you were starting to accessorize with girl’s ribbons.” Riza retorted, shoving his knees into the couch as she made just enough room for herself to sit primly on the edge of the seat cushion. “I need that back, _and_ my bra.” 

“I know. That didn’t fit in my pocket.” Roy said with a laugh. “But you didn’t ask nicely.”

Riza’s brandy eyes narrowed, and she glared at him, pursing her lips. Coercion was rarely a successful method of making Riza Hawkeye do anything - and on the whole, Roy didn’t attempt to try. But this time, it seemed worth it to tease her just a little. Pinching her pink lips together for a moment, she frowned, before looking away. “I wonder how upset my father would be if I told him you’ve been nicking my things.” 

“Less upset than he’d be if he realized you left it behind in my room after you removed your blouse.” Roy said helpfully, pulling the ribbon to his chest. 

“If I could write a list of the things Roy Mustang, alchemy apprentice and general arrogant pretty boy gets away with, I’d probably be able to make a book of it.” 

Greeting her with a dangerous smile, Roy leaned in conspiratorially close. “Chapter two, Roy Mustang, arrogant pretty boy, and the time his Master’s daughter let him feel her up in the his bedroom…”

Leaning in as if she had decided to kiss him, Riza set a hand over his shoulder, before she reached over to snatch back the silk black tie from his hands. The loose bow unraveled as she grabbed it, and Roy was quick enough to catch the other end of the ribbon, and wrap it around their hands, lightly pulling her a little closer. 

Riza tried not to show that she was amused - it would be better for him if he was a little more disciplined. “ _Let you._ ” She warned, tugging back on their hands as she tried to unwind herself from his knotting. 

“Allowed me,” Roy conceded. “-the distinct pleasure of fondling you.”

“See if it happens again if you keep that tie.” Moving her hand, she found the ribbon unraveling around her before Roy moved again, quick to this time clasp her hand as he did so. Without much warning, Roy had moved to kiss her openly, less sweetly and more of an impish move that was meant to distract. Before she could even bother to sound out a noise of annoyance, Riza relented, _solely_ , she told herself, _on account of the fact that Roy was likely to give her tie back as soon as he was done kissing her so nicely._

It was rather hard to see how Roy was such a good student when he procrastinated so often, but Riza had decided there was a method to Roy’s madness. Claiming he worked best under pressure - _a metaphorical fire under his ass_ \- Roy often worked on his assignments and studies at all sorts of odd hours. And when he did bother to crack open his books, he was easily swept up with distractions like his gentle caress of the inside of her wrist as he slipped his tongue neatly into her mouth, eagerly meeting her lips. The fact that he still seemed to retain and process all the information he had been learning was no small feat. Riza sometimes suspected he had perfect memory, but even that seemed like too much credit for Roy Mustang.

 _No_ , she considered as he pulled back a fraction, waiting for her to follow him _, Roy was just simply that good._ The fact that he knew that was why, well, it was infuriating sometimes.

Shifting, Riza tilted her chin slightly, using her free hand to slide the alchemy book and his notes from his lap, setting them against the floor as Roy moved to make room for her. Without further ceremony, Riza straddled his lap carefully, her navy pencil skirt riding up her thighs as she sat over him, making for easier access. The suddenness of the movement and the very definite and demanding weight to her presence caused Roy to grunt in surprise, hands slacking his grip just long enough for Riza to slip her tie from his hand. Breaking their kiss to laugh quietly, Riza looped the ribbon under her collar as she leaned back on his hips. Roy shifted underneath her as she finished her neat bow, somewhat crestfallen that she’d retrieved the tie. 

“Well, I did ask you nicely that time.” Riza said, catching his petulant expression. “You should have just given it back.” She added, angling to kiss the soft spot directly under the side of his jaw. She could feel his pulse flutter under his skin for a moment before she dropped her lips further down the column of his neck. When he spoke next, wrapping a hand in her hair, she felt the vibrations of his voice. 

“I was using that as a study aide.” He said, tone less upset than he’d originally intended for it to be as she unbuttoned the top of his collar and pressed another kiss into his collar. 

“I fail to see how articles of my clothing improve your concentration.” Riza replied. 

“It was a very significant help for my research, which you have interrupted for another round of theoretical implementation.” 

“Hands-on…?” Riza asked, kissing him firmly as she draped her arms over his shoulders. 

“Book knowledge only goes so far. At any rate, I finished organizing my data tables and the key, so if you’d care to double check my work…” Roy said, reclining further into the couch as he looked up at her playfully, tugging the end of her bow. A page of notes slipped from his haphazardly placed notebook, and crinkled across the floor with Roy’s unmistakeable looping scrawl. 

“Maybe later,” Riza said, pulling him up into another kiss.


	3. Chapter 3

**Notes for the Chapter:**

> Late June, 1903. Ashford, Eastern Amestris.

Twenty minutes before Riza’s father was expected to arrive back at the manor, Riza’s bow had been re-retied, her blouse buttons closed up, her skirt smoothed down, and her hair tousled back into a messy look that looked somewhat like it had been done on purpose, instead of by a handsy teenaged boy. She had left Roy on his own to adjust himself back into presentable shape, snatching his note pages and one of the shortbread cookies on the end table before she calmly slipped out of the room and went to reapply her lipstick. It wasn’t so much about fleeing the scene of the crime as it was an intense curiosity as to what he’d written down in his ‘notes’, coupled with a way to disguise the freshly bitten look of her lips. 

Ten minutes before Berthold Hawkeye was expected to arrive back at the manor, Riza would be found in her room, heady blush almost gone from her cheeks and a prim pink adorning her lips as she appeared to be nose first in a lengthy history text about Ancient Xerxian politics. Riza really had been enjoying the book for the past week, but in the slightly disquieting circumstances that her father would bother to drop in her room to inform her about something that had happened on his trip, she would only appear to be reading it. 

As it so happened, Roy’s notes had been folded neatly into the crease of her book, the lean lines covering paragraphs about the Xerxian Empire. And instead of reading something about the Emperor’s role in religious rituals as it related to politics, Riza was blinking down at a rather funny little set of chemical compounds and random elements. 

If she didn’t know any better, she would have said Roy had failed basic chemistry in grammar school. Since she did know better, the ridiculous organization brought about a second look. 

Across the top was a row of long hand elements written out, in some sort of order Riza hadn’t quiet figured out the method for yet: _Molybdenum, Boric Trioxide, di-Hydrogen, Chlorine, Cobalt, Silicon._

Underneath that was a additional, squeezed in column, that seemed to cross-reference the top, this time in shorthand _: K, H2, Cu, Li, Fe, S, Bi, {Electron stabilization + Covalence}._

 _They were all cross referenced,_ Riza realized. Molydbenum was checked with potassium, lithium, and bismuth, and Riza’s brow furrowed as she tried to figure out why ever someone would combine them. A neat arrow referenced the unfinished balancing of an equation, giving her the combination _Mo+KLiBi_. 

Riza didn’t have a head for science the way Roy did, or the way her father wanted her to have, but even she knew she was looking at gibberish. How he thought these notes were helpful, she wasn’t sure. Another line gave her a secondary unfinished equation −- _Bo2O3 + KH2Cu._ Flipping the page over, Riza examined the rest of the paper. There wasn’t much else, a few more scribbles, and a scratch out here or there in his writings, a space left empty for the parameters of the exercise, and a word for word chunk of a text on covalence. _“When two non-metallic elements bond, they often share electrons, known as valence sharing, or covalent bonding. These atoms will share a sufficient amount of electrons in order to achieve the electron configuration of a Noble Gas.”_

Then nothing else. 

She leaned back in her bed, sinking into her pillow as she sighed in aggravation. It wasn’t chemistry. And it wasn’t sensical. And while she wouldn’t put Roy making everything up just to mess with her out of the question, she had a distinct feeling it was a code that she needed to break in order to understand. The idea that Roy Mustang was just down the hall, probably laughing to himself over her pilfering his codes notes made it even worse. 

So Riza did the only thing she could think of to do; she hunkered down to crack it.

 

For the next three days, Riza spent her free time in her room, working on Roy’s notes only when she wasn’t busy trying to convince herself attempting it on her own was a waste of her time. Would have been a waste of her thoughts too, as Riza didn’t much care for the idea of pining after a ridiculous little note page. Roy’s codes weren’t anything new, in the time they’d known each other she’d picked up several of the differences between what he said aloud and what he was hoping she’d know he meant. 

The first code, the easiest, was the most subtle. Instead of spelling out loud words, Roy told anecdotes, regaling all sorts of stories of mischief, hijinks, or propriety and a scholarly countenance depending on his audience. But he used names to code his messages, usually the names of people but occasionally places; names of customers, accountants, loan sharks, professors, generals, secretaries, call girls, ballet dancers, actresses, and bakers. If there was some way to work them into his colorful stories, he would. And it didn’t take long for Riza to figure out that he was spelling things - Roy was careful and precise about the order of his stories, and had seemed to be doing it just because he thought it was clever, and needed practice with it. For Riza’s part, she had written one of his stories out using a quick shorthand she’d picked up in school for improving memory. The fact that the emphasis had been on people and places had made his message obvious had been a bonus. 

As soon as he’d realized she’d cracked the code, Roy had excitedly made it a game. He made it increasingly complicated, letting Riza reply in her own stories, sometimes with shared memories, sometimes with brief summaries of serializations in dime store anthologies she picked up to read in her free time. They’d begun to gain a knack for communicating without the outside world picking up on their words. But this time, and with this particular code, even with three days of ignoring Roy Mustang’s passing smug looks, she still hadn’t cracked his exact meaning. 

Which meant that when after dinner on the fourth day, her father went to lock himself in his study after an aggressive quizzing of Roy’s studies over their plates, Riza had the young alchemist cornered. They had made their way out of the dining room without much fanfare, but as soon as they rounded the hall towards the staircases, Riza’s hand had darted out to grab his wrist and pull him to the alcove under the winding staircase. 

“That had absolutely nothing to do with chemistry.” She accused firmly, trying to keep her annoyed expression affixed to her face despite the general eagerness glinting in Roy’s eyes. The corner under the stairs was poorly lit, but even still she was able to make out the slight curving of his lips and the way his dark lashes stood out against pale, vaguely Xingese skin. 

“Didn’t it?” Roy said, licking his lips instead of laughing.

Brow furrowing, Riza leaned back, squinting at the way the light of the hall draped over his shoulders. It’d been straight from the elemental table, but the underpinnings of it had nothing to do with science. That, Riza had been sure of. “You chose specific elements to represent things, and then created nonsensical balanced equations to communicate.” She said slowly, as she collected what she had bothered to figure out from the page. Slipping his notes from her pocket, she held them folded up between them. Roy stepped closer, holding her wrist to his chest as he slipped the pages from her grasp with his other hand. “Then you expected me to relate this to your grand experiment…” 

“Ours.” Roy corrected, rubbing his thumb over the back of her palm. “At any rate, I thought it would be rather obvious. But for your benefit, I’ll give you a key to the code.” A shuffle of papers placed his notes back in her skirt pockets as he leaned to wind himself closer to her, pressing Riza against the far wall underneath the stairs. “Molydbenum, reactive to potassium, lithium, bismuth.” 

“That doesn’t,” Riza began, before she was cut off by Roy’s mouth covering her own. His lips were warm, like heat of the sun sinking in the sky outside. It was languid, and Roy took his time in moving his mouth hungrily against hers, pulling on her bottom lip playfully as he wrapped an arm around her waist. Commentary lost to his mouth, Riza moved in on him, honing in her focus on Roy’s words as much as she could. It wasn’t easy as she would have liked, especially as his hands kneaded firmly into her sides, tongue sliding between her parted lips. When he wanted to be, Roy Mustang could be terribly distracting for other people’s concentration too. 

A few minutes passed of them simply kissing underneath the stairs, fueled with an edge of urgency as they both realized eventually they would need to be in other places before people looked for them - or before someone found them. But Riza couldn’t say she was too worried about being caught - Roy Mustang was a perfect scoundrel. He was as good at stealing moments as he was breaths and thoughts and she had the sneaking suspicion she rather _enjoyed_ helping him get away with it. 

When they finally broke apart, Riza licked her lips as he peered down at her with the same blue-black insatiable hunger in his eyes as before. It wasn’t an intimidating  hunger; rather, it was the sort that was laced with some level of kindness and affection that Riza was sure she shouldn’t dwell too closely on. They were good friends, and it was wonderful to kiss him, and to break his codes, but thinking too hard about it wasn’t her style. 

“Molydbenum — mouth? And potassium is K, for kissing.” Riza said, worrying her bottom lip between her teeth as she leaned back to gaze at him as she traced the line of his shirt collar. “So that makes lithium to lick, and bismuth to…bite.” 

Roy kissed her nose before he slipped his arm away from her waist and pulled back. “See, you’ll figure the whole code out. I knew you would get it.”

“That’s still not alchemically sound.” Riza scolded. 

“I beg to differ. We’re full of chemistry, you and I.”

**Notes for the Chapter:**

> Reviews and Kudos are _highly_ appreciated! Stay tuned every Monday, everyone. We're already half-way to the end!


	4. Chapter 4

**Notes for the Chapter:**

> July, 1903. Ashford, Eastern Amestris.

“Do you mind if I try something?” Roy said, voice sending vibrations through her ribcage as he spoke. It had been weeks since their interlude under the staircase, and even less time since several other of their rendezvous. This time, however, they had the promise of an entire day to themselves, and an elementally based code of trial and error to base a rather large amount of conclusions off of. Roy had settled against her bare chest again, cradling her in his arms as they tangled together on his bed in his room.

She shook her head no, on the whole feeling rather pleased with how things were going so far. This was Roy, after all, and he had been nothing but wonderful - not just as a person, but he made her feel good. Safe, if she had to put a word to it.

“Like what?” she thought to ask. “I mean, I liked what you were doing before.”

At this, the tips of Roy’s ears pinked under his pitch black hair. It seemed sort of pointless for him to be the one blushing when he was clearly resting chin first on her chest, but Riza pushed that thought into the back of her head, and leaned, looking at the way his shoulders tensed and his muscles rolled under his skin as he breathed. “I was going to continue kissing you.” 

The statement clearly should have meant something more, but Riza just stared at Roy blankly. She tilted her head. 

“Everywhere _else_ , this time.” Roy said, to clarify the matter. A thick rush of warmth returned to her insides, and Riza became keenly aware of the reason why his kissing her knees earlier had seemed so overwhelmingly nice. Everywhere else. That…that sounded good. Giving him a small nod, she stopped to admire Roy’s sense of imagination. It could come in handy, that.

In the back of her mind, she distinctly remembered that it did come in handy - especially for the studying he was supposed to be doing. 

But books were long gone from her concerns, and it seemed worth it to claim this was also a part of his scientific process. Everyone needed few laboratory experiments after all, and Riza had it on good authority Roy’s experiments were better suited for her than for anyone else who might be skulking around the Hawkeye household.

She fought another laugh, before Roy’s head dipped to her chest again, trailing a determined pattern of kisses down her abdomen and to the sharp corners of her hips. He’d returned his warm hands to the small dip of her waist, and she shivered as he licked a teasing line on her hip.

It was beginning to become obvious that Roy really enjoyed when she dug her hands into his hair. The sound Roy made in response to her hands was somewhere between a cat’s purr and a rumbling groan that tickled against her skin. Riza didn’t think herself particularly self-conscious, but she thought it was a little bit embarrassing that he was reacting like that when she was the one stripped to the waist, and he was the one doing something fascinating with his mouth and the hem of her skirt’s waistband. He hesitated, and Riza wondered briefly if he had lost his nerve. Her fingers curled, and Roy made another noise that felt a little obscene. But then, all things considered…

Panting a few times, he gathered his breath again before he started to ease her skirts over her hips, and Riza tried very valiantly to not give him more directions about his pacing. She suspected that the slowness of it all might’ve been for both of their benefits, and really, while she felt a knot that tightened like impatience somewhere under her skirts, she thought it best not to tell Roy just yet. It was all a matter of getting there eventually. 

“Did anyone ever tell you about the theory of evolution?” came Roy’s reverie interrupting comment as he pulled her skirts over her thighs. 

 _Alchemists_ , Riza thought. “Are you trying to study?” Riza said, giving him a narrowly disapproving look - the kind she normally used when he wasn’t paying a lick of attention to his work to begin with.

“No, just…” licking his lips, Roy bowed his head kissing her left knee sweetly. It sent a shiver down Riza’s spine, and she smiled at him again. “—there’s a part about ‘endless forms, most beautiful and most wonderful have been, and are being evolved’. I thought of you.” Moving his lips from her knee, he gave her a soft sort of look, admiring his view for a moment. 

Unsure of what to say, Riza leaned forwards to brush his bangs out of his eyes; he meant her, of course. Roy wasn’t the poetic type really, he was an excellent speaker, she’d heard him before, but recitations were different than using his own words. But this was genuine, and deciding that she liked being a woman of few words, she kissed him gently on the bridge of his nose in thanks, before dipping her head as he pushed himself up to meet her mouth. 

It was wonderful to return to the kissing, to feel the way her chest pressed into his, without layers of clothing between them, without the same barriers as they usually had. It was more than sweet; Roy’s mouth was warm and felt more demanding than it had before, and Riza lifted her hips eagerly when his hands went for her underwear. Shimmying, she pushed away from the headboard, sinking into Roy’s pillows as he broke their kissing to crumple her underthings in his hand. 

If Roy Mustang thought he was going to end up holding Riza Hawkeye’s underwear in his hands, he certainly didn’t look like it. He blinked at the offending light blue fabric, before tossing it aside on the bed, and settling down between her legs. Studying her for a long moment, Riza watched his expression in turn. “Are you okay?” she asked hesitantly. 

Roy nodded his head. “Fine. Just reconciling theory with practice.” He said quickly, looking up at her stubbornly. 

Riza nudged him with her knee. “What sort of theory on this do you have, anyways?” she demanded. He was beginning to look a little daunted. But before she could chalk it up to nothing more, Roy returned her look with a mildly affronted one. 

“My sisters talk. They keep around a lot of romances, so I’ve heard a few things. It’s really not that complicated, I just don’t want to miss anything important.” He defended. 

Sighing, Riza nodded. “You should probably start up a little, get your bearings. Work your way down.” 

Roy blinked at her in surprise, before she made an exasperated sound in the back of her throat. “I think I have a little more practical theory than you do. Just don’t bite me.”

“I would never.” Roy said looking mildly horrified before he hooked her leg over his shoulder. “Hey,” he said, as if another thought had struck him. “Give me your hand.” He instructed, waiting for Riza to slide her fingers under his palm. Squeezing gently, he placed their hands at her hip, as one last reassurance before he bowed his head and kissed her thigh, once softly, and then further up to the spot where her leg met her hips more firmly. When he hit the vee of her legs, he nudged his nose gently against the folds of her skin, waiting for Riza’s reaction. 

“More,” she began to direct, stopping short as Roy took his other hand and slid it between her legs, cutting her voice off with a squeak of pleasure. The feeling of impatience grew, and she felt herself heat up all the way from her cheeks to the very spot Roy was was now dutifully kissing with closed lips. Fisting her free hand back in his hair, she pulled Roy closer to her hips, cradling the back of his head as she felt something that Riza was fairly sure was a smirk - that idiot - before he opened his mouth. 

Testing his placement, Riza began to understand why Roy seemed to practice kissing with tongues so much. She hadn’t given much thought given to its other uses, but now that he was demonstrating, it made perfect sense. Taking her advice, he had started from the top, laving his tongue over her gently before he followed his fingers downwards. The motions reminded Riza of the way Roy had licked the hand cranked strawberry ice cream off of his spoon the previous summer, with the naughty relish he usually had when he was indulging something. It had only been a taste for sweets then, but now… 

The dedication spoke to something else, and not his love for strawberry, or sweets. 

It was wonderful, but, “-stay up.” She decided firmly, deciding his mouth was better suited to a smaller area for the time being. Heeding her commands, Roy tilted his chin, and moved his tongue. It took a few passes before he figured out the right movement for her, but when he did she moaned in appreciation. Riza propped her other leg over his shoulder, locking her ankles over his back, angling for a better swipe of Roy’s tongue over her clit as he tried something that went in a circular motion. 

“ _Oh_.”

Whatever happened next, Riza was grateful Roy didn’t try to bring up melting points as a way to tease her about the amount of sinking into his bed she was doing. Making a few more pointed comments, Riza guided him in the right direction, before she forgot about speaking entirely and returned to gasping as Roy attempted a variety of different things. He’d begun to use his fingers more, moving one inside her before he got a feel for working his mouth and fingers at the same time. Roy shifted where he lay, moaning into her skin for a moment before he collected himself at Riza’s nudging with her legs. 

Adding a second finger, Roy put a more concentrated effort on the quickening of Riza’s breath, and the clamping down feeling of anxiousness for something to ease her growing need. If anything, Roy’s fingers and mouth had made her squirming impatience worse, and she arched her hips up to meet him, shivering as he moved his tongue over her flatly before tracing lines into her skin. Riza squeezed his hand more tightly, and Roy fumbled against her slick skin to keep up, getting a little bit more firm as she gasped sharply. Moving his fingers up against her, curling them as he pushed into her, Roy stepped up to a pace that was thoroughly employing his fingers and mouth together. Riza’s stomach tightened and she felt another rush of wetness cover his fingers as he crooked them again and pressed up, sucking gently on her clit as he attempted to keep up with her twitching hips. Inhalation hitching, Riza’s breathing took a sharper, more urgent note as she pushed back into his mouth and hand. Another shivering vibration caused her to tense as Roy moaned again when Riza tightened her grip on his hair.

It took a few more minutes before Roy’s movements found another good rhythm. When he did, Riza tilted her head back into the pillows and snatched his free hand at her hip, clinging onto him, as her body trembled with a warm and bright feeling that had pulled her taut in a peak of pleasure. For a moment, Roy’s mouth and fingers kept moving in perfect concert, spinning the world into a white hot pin point that had Riza arching off the bed. Her orgasm struck sharply and strongly, and without a second thought Riza gasped and cried out as it peaked, leaving her shaking around Roy. She moaned, shivering as the world began to right itself, the snapping of the tension in her body caused her to settle loosely back onto the bed like one might unwind a knot.

There was another moment of quiet silence as Riza adjusted herself back onto the bed comfortably, while Roy removed his fingers gently, leaving her feel distinctly less full. The idea of another blush played in her mind, but Riza was fairly certain it wouldn’t be something he would even notice under the flush of her orgasm. Roy kissed her lower belly once, in a way that felt strangely chaste in comparison to everything else before he leaned up to meet her eye to eye. 

“ _Wow_.” He said, with a hint of admiration. 

Shrugging her shoulders, Riza closed her eyes and shifted further into his pillow. “Shouldn’t I be the one saying that?” she said quietly. There was a sound that indicated Roy had moved, and a rustling that sounded like he had peeled out of his pants before his weight sank the bed as he laid down beside her. When she opened her eyes again, he was giving her a lopsided grin before he quickly pressed a kiss to her cheek. 

“I dunno, should you?” he asked quietly. When Riza realized he wasn’t just teasing, and was honestly asking what she had thought, she smiled slightly, before rolling to her side and burying her face into his collar. 

“I think we both should.” she said finally, smiling against his skin as he wrapped an arm around her. 

“I like that.”

**Notes for the Chapter:**

> Much thanks to everyone who has reviewed and given kudos so far! I really appreciate it, everyone!


	5. Chapter 5

**Notes for the Chapter:**

> Late August, 1903. Ashford, Eastern Amestris.

As summer wound down, Roy began to look more anxious. Not about them, Riza knew, but about something else. Something she hadn’t quite been able to place. He’d received a letter from home that he’d hidden away amongst his things without discussing it, and whatever its contents had been had changed him somehow. His morning runs became longer, his exercise routines more intense. It had nice side effects: Roy would come back blood rushing and already panting and Riza would pull him into her room for experimenting of her own, but it also meant they had less free time. It meant that something was also stressing Roy. 

There had been more tense conversations at the dinner table when her father had bothered to grace the table. Usually, Roy danced around the subject of flame alchemy as gracefully as any fencer. He knew when to parry and when to thrust, and had more often than not feinted in another direction to ease her father’s temper. But lately, it had seemed like Roy himself was impatient; he’d lost the finesse of his wheedling. Now, his strikes were blunt and more forceful - which had done little to convince Berthold to change his mind. 

Roy simply wasn’t going to be learning flame alchemy yet. 

But Roy’s increasing sense of impatience had Riza wondering if he had some sort of imposed deadline he hadn’t mentioned. Something was looming over Roy that wasn’t the usual eastern storms of late august. But whatever it was, she hadn’t quite figured out the right moment to bring it up. It felt silly to complain that he hadn’t already told her what was wrong. Worse, Riza had felt foolish for assuming she should have been able to simply look at him now and understand him wordlessly. They’d grown comfortable with each other’s signals. It felt as if she should have been able to tell by the determined glint in his eyes, or the half-hidden sadness his body would take on as he pulled her close to him and buried his face in her cropped hair. 

She wanted to know - because he told her outright, or because she understood the words his body spoke for him. But no one time had seemed right to ask until her Father left for a weekend trip to obtain a particular piece of important research materials for his ‘manuscript’. 

Their Friday afternoon alone had been rather unremarkable, but Saturday evening Riza had found herself in Roy’s room after a particularly fervid moment of study. Now that the servants were also gone, and they were completely alone, Riza took the opportunity to lean over him carefully as she settled in his bed. She nestled her chin in the notch of his collarbone quietly, watching him lose himself to deep thoughts. A frown worked its way across his features the longer his silence held, and eventually, Riza looped her arms over his shoulders. Fits of silence and alchemic theory weren’t unusual, but now she was beginning to worry. 

“Are you going to tell me whatever it is?” she asked softly, breaking his reverie. 

Tipping his head forwards, Roy hung his shoulders. “I didn’t know how. I was hoping I would figure it out properly first,” he began, looking away from her for a moment. Riza’s eyes darted to the corner of the room he had directed his attention towards, landing on his trunk in the far corner of his room. Then she looked further, to his now empty bookcases. It didn’t take much reasoning to assume that if she rifled through his dresser drawers or the armoire, those would also be mostly empty. Her stomach sank.

“When I went home for my birthday, I spoke with a recruiter - well, a General, actually. Someone my Aunt knows. I told him I was turning eighteen, but that I was studying alchemy…” The rest, Riza already knew, but she let Roy continue anyways, trying to keep her expression calm, impassive. “What with the unrest on the Eastern border, they’re really looking for more men. To make a long story short, I applied to the Officer’s Academy in Central. I passed the exam with flying colors. Well, I scored a perfect, really.” 

At that, she smiled softly. Of course he had scored perfect marks. Anything less than wouldn’t have been Roy Mustang. Still, Riza held her tongue, and waited for him to finish his explanation. “It starts in September, next week. They’ve given me a scholarship to attend, this General really seemed keen on me when I mentioned my studies, and I thought…it’s my duty to, you know?”

Duty. Riza almost felt like pulling a face, but she understood, more than anything else he might have said. Just as much as she had a duty to her father, however strange or distant he could be, she had developed a sense of duty to Roy, to his learning, to invoking those once in awhile genuine smiles that slipped between his knowing smirks. Of course she knew. 

 “Your father doesn’t want to teach me Flame Alchemy, but I still have to be useful, somehow. I could really help people. Just knowing a lot of things doesn’t make me useful. There’s more important things than what’s in my head - serving my country, protecting people...” He said, voice gaining in confidence as he spoke, a layer of happiness and certainty spreading across his features. Riza wanted to argue the point, wanted, briefly, to tell him that books and knowledge were of the utmost importance for society. But even she didn’t believe that was the whole of it, and it was harder knowing she agreed with him. Books - knowledge and learning - had made her father the man he was. Roy was meant for something other than just that, and she had known very early on that he intended to do something more than what her father expected. 

Pausing, Roy bit his lower lip. “I didn’t get my acceptance letter until earlier this month. And when I found out, I wasn’t sure how to tell you. I have to tell your father when he gets back…I’m sorry.” 

Silence fell between them again, and Riza breathed in and out easily as she considered the announcement. It was strange to think that the body beneath her fingers would soon be gone completely. And it didn’t feel fair. He was leaving to do something more with himself, and she was left here, alone with her father once again. Perhaps back to secondary schooling for the year, but otherwise left to her own devices. The idea of not having something of her own in mind made her wonder what she should be planning for herself, but she didn’t bother to voice her concern. 

Instead, she said what she thought was more appropriate for Roy to hear. He knew already how her father felt about the military, and he was already set on what he was going to do. Which left her one thing, “You could have told me sooner.” 

“I should have.” He admitted. 

“You’ll be good at it.” Riza said firmly, brushing a messy lock of hair from his eyes. 

“You’ll miss me, won’t you?” came his response, eyes alight with bared concealed worry. For the first time in years, they would be genuinely be separated. If nothing else, they were certainly close friends, but now, there was something else between them. Whether it was nice or sad to realize, Roy cared about her, and what she thought. 

“I don’t know if I’ll miss your procrastinating.” Riza said, trying to ease the sudden mood between them. “But you, maybe.”

“I’ll miss you, and this.” Leaning, he kissed her lightly to emphasize his point. 

“I don’t think I like the idea of waiting around, though. I don’t want to be one of those girls who sits and waits for a soldier.” 

This comment seemed to fluster Roy, who shrugged. It was clear he had expected something else, but what, Riza wasn’t entirely sure. She’d seen, and even commented, on the girls in town who engaged themselves to young men who intended to leave, and sent small checks from their pay home. Girls who wore flowers pinned to their blouses, or small green ribbons in their hair to remind everyone they too served the country by remaining strong. It was too much, it wasn’t her, and it made her frown to think about it. 

“Of course. I mean, I wouldn’t want to worry you. It’s just school.” 

“You’ll be too busy to think about me,” Riza said. “And I’ll be too busy to fret about the boy who scored a perfect on his exams.” That was the sort of relationship she would be alright with. Perhaps that was why it hurt, knowing that she would have to part ways. Dwelling on Roy Mustang, when he was intending to be in the Military Academy would be too much. And maybe he would find a nice young female cadet that would make the separation irrelevant. It was unfair to keep them both waiting on something. 

Still, there was something else to be addressed.

“What a shame that we never finished our research.” She said softly. 

“Hmm?” Black eyes blinked up at her curiously. 

“I cracked the rest of your code. We never— you left out the covalent bonding aspect of the code. Never added anything to the notes. I noticed.” It hadn’t been hard to make a leap of assumptions as to what covalent bonding meant. He’d never elaborated on the issue, certainly never brought it up aside from writing it down on the notes page. But Riza couldn’t help but think he was being in his own way, a bit of a romantic about it. 

“It wasn’t just that. I mean, covalent bonding—“ Roy began to explain, face somewhat hot from the suggestion. 

“I know. But that’s a piece of it, isn’t it?” she laid her head down against his chest again, listening to the soft squeeze of his heart beat beneath his chest.

“It can be. I didn’t want to treat it like it was just something else we did because…” 

Roy’s words died out as Riza’s fingers moved to his shirt collar, unbuttoning his shirt and peeling it away. “Isn’t covalent bonding sometimes inevitable, with the right elements?” She asked calmly, eyes concentrated on the smooth lines of his collarbone. 

“Not inevitable,” he breathed. “-Just highly likely based on electronegativity and—“ Riza leaned, kissing the bared spot of his skin to cut him short; kissed his throat, and then his mouth, warm and wanting. The words weren’t important, she found, and the reasonings weren’t either, as long as they both understood each other. 

“It sounded nice.” Riza whispered as she broke the kiss. “Atomically.” 

“Sharing electrons?” Roy breathed heavily, half lost to her change of topic and half lost to her. 

“Something like that. Sort of like we could fit.” 

This had him leaning up to prop himself up on his arms, Roy’s hand falling to the small of her back as he shifted. There was a long moment as they looked at each other in anticipation, the edge of a tipping point that Riza wanted to push them both over. If there was someone she had wanted - the way her schoolmates had read about in their romances - it would be Roy. 

“I—“ Roy started to say, before stopping short as if he had thought better of whatever he had planned on saying. Instead, his eyes flicked to his nightstand, and he swallowed, clearing his throat. “-I’ve got things.” 

Nodding, she pushed off of him, kneeling beside where he had been laying down as he reached for the drawer of his nightstand. There wasn’t any need for further explanation, Riza knew that this hadn’t exactly been a surprise topic. They were both too young to deal with any unwanted consequences, and it was clear that Roy had taken the potentiality of them seriously. He rescued a small waxy envelope from a metal tin, and set it aside, looking back at her intently.

The air took on another nervous, bubbling feel and Roy settled to kneel back before her. Without meaning to, Riza chuckled nervously as he did away with his shirt, dropping it to the foot of the bed. “You sure…?” he asked, as she reclined back over his comforter. 

“Yes.” There wasn’t much else to say besides that, and Riza pulled her blouse up over her head, slipping it to the floor as Roy settled between her legs and moved to kiss her. It wasn’t hurried, but Roy was intent on covering as much of her body as he could, unhooking her bra as she leaned to meet his lips, sliding away fabric and modesty. Hair tickling her chest as he pressed on, Riza laughed again, this time breathily as he smiled into her body, nipping and teasing as he went. It took on a staccato rhythm as he moved, lips pressing to her belly before they found their way to her hips and then again at her breasts - an invisible constellation of him across the spaces of her body. 

When he returned to her lips, the devotion of his enthusiasm became clearer. Happiness, Riza decided, was the only thing that could blot out fear, trust the only way she could push the idea that soon, she would lose this. Lose him, for a little while. And while elements could covalently bond with all sorts of other objects, while she could find this elsewhere, at the moment, it felt as if there was only one person with which she wanted to connect. Things would change, she knew. They would change, and bonding wasn’t about sex - 

\- But when she saw the look in his eyes, and knew that she shared the same desires, she couldn’t help but feel like it was a place to go with it. 

Her mouth opened for him, straining to meet Roy everywhere he was; to feel and pull down all at once. The impatience knot returned, the fiery burning desire set deep within her skin — forget alchemy, Roy set fires with his body alone - and she reached to help push her skirts off her hips. Between them both they made each other more fervent, hungry and searching. Her fingers slipped down over his back, feeling out the strong, hard lines of muscle that lay there. Exploring this was nothing new, but time, and freedom, and loneliness without each other was setting in, and _this_ was different. 

Luckily, Roy himself was not. 

Neither of them had favored any particular religion, but Roy’s dedication to the apex of her legs, the strong lines of her thighs, had begun to border on religious. She had thought, once in awhile, that she should tease him about his kneeling before her, his enjoyment and her pleasure being some sort of ritual for them when they stopped, when they could have the time — but Riza had held her tongue. Whatever it was, it was better left as an inside joke with herself that kept her quietly amused until his mouth caused too much of a distraction for her humor to be her focus. 

While his technique had certainly improved over the summer, it was enthusiasm that made her feel electric, carding her hands through his hair as he sweetly nuzzled her thigh before moving to turn his tongue to her. If there was something she had to hold to herself, a secret she would gladly keep, it would be the movement of his mouth against her folds, the teasing flicker he’d figured out made her twitch with desire. 

Roy’s fingers were another story entirely. In books, Riza had read details of the pain of taking a man, but it seemed quite unrealistic in her small wealth of experience. The sensation of his fingers had started out as more than sufficient in their own way, and Riza knew that when he moved she would feel it. As they’d returned to this moment, however, Riza had found that dealing only with Roy’s fingers had become maddeningly teasing, enough to make her wet, but left her still wanting to feel more. If it hurt, she supposed it was because of an unreadiness - or, she thought wryly, perhaps a failure on the partner’s behalf to be perceptive of the adjustments necessary. 

 With Roy, three of his fingers only made her want to grit her teeth and scream. The tip of his tongue slid against her her clit and Riza arched on the bed, gasping desperately. “ _R-roy_ _Mustang I swear if you_ —“

He pulled away suddenly, the heat of his mouth vanishing and his fingers leaving her as he popped his lips and gave her a _look._ “What?” 

“You _stopped.”_ Riza said, shifting her hips beneath him. 

Roy chuckled, leaning up to kiss the side of her neck as he lightly brushed his thumb over her clit. Gasping, Riza shivered as she began to breathe heavily, a whine ready to break from her throat. The build up was maddening, no matter how much she enjoyed it. 

“Give me a minute, I promise to take care of that.” Came his reply as he pushed away to fumble with his pants. 

She gave him no rejoinder in return, instead pushing herself up to help him peel off his pants and then his underwear, slipping them over defined  and narrow hips, freeing his erection from its confines. Riza smoothed her hands over the soft spot just over his hips. The actions brought to memory the way she had kissed him there before, tongue snaking over the juncture of his hips and the lines of his body. This time, however, Roy was more intent on rolling on the condom than he was on encouraging her hands to wander, and Riza bit her lip in expectation. Her fingers pressed into his hips gently, and in a moment, Roy was done, kissing her lightly on the mouth once more before he nudged her into leaning back onto the bed. 

“Ready?” He asked, bumping his nose against hers lightly, as he began to position himself between her legs. His hands moved to her hips. Riza shifted, rolling her hips up to meet him as he brushed against her. 

“ _Yes_.” 

It was slow, careful, but Roy kissed her before he rocked gently, pushing against her. The adjustment took a moment, and Riza’s hips swayed with the weight of his body and the the way he felt with her. The concentration in Roy’s eyes turned them sharp like obsidian, concerned and desirous at the same time as he sunk down. Riza’s hands twined over his back, fingers pressing into his shoulders as she panted. It didn’t hurt, but the pressure was new, and she breathed in deeply before catching Roy’s gaze. 

His expression had made her feel more exposed than anything else thus far, and Riza flushed under the intensity of it. Nodding, she encouraged Roy to move again, the sudden flush of ache now that he was remaining utterly still overthrowing the other slight discomforts. Testing their position, Roy rolled his hips, thrusting gently as he kissed her collar. 

Their pace was uneven at first, but Riza already felt as if she was on the edge of something, and when she rose to meet him, Roy bit his bottom lip. Something light bubbled up in her throat, but instead of laughter, Riza moaned appreciatively as Roy evened out their rhythm, picking up the pace. He was breathing raggedly, exhaling hot against her ear before he kissed her with abandon. Slipping a hand between them Roy rubbed her clit as she arched up into him. 

Riza tightened her grip, fingers pressing harder against his skin. The same need filled her from the inside out, rising up from where their hips locked and legs tangled to her heart beating faster in her chest. 

The lines of his shoulders above her blurred as they twisted and moved, Roy’s moans rolling over her, vibrating from within his chest. Between them both it was enough for them to be like this. And while it was finite, the desire to pull him down with her, to lock and meet over and over again felt like it would last - until she tilted back and let Roy’s fingers in tandem with his thrusting push her into a frenzy. It wasn’t like her orgasms from before - this was different and tighter, running up the base of her spine and curling her body into his, hips working desperately to take him in as she let senselessness take over and her body work on nothing but raw instinct. Gripping him tightly, Riza rose and fell again and again as Roy met his own moment of completion, tight control slipping from his face and ripping a warm rich sound from his throat that sent another rolling shiver down Riza’s spine. In ecstasy, Roy looked beautiful - hair sticking to his forehead where it had become damp with sweat and face free of its usual barriers. He slowed when he was done, stopping to catch his breath and to kiss Riza’s shoulder. 

With great care, Roy slipped away slowly, almost too tired to move. Riza closed her eyes as she winced at the change again, letting him toss the used condom into the trash before he returned to her side, still panting and exhaustedly kissing her neck. The air had changed, it was warmer now, sticky, but in a way that made Riza feel as if a nap would drag them both down before anything else. Her lashes fluttered as she considered moving on her side and resting her eyes. Roy kissed her forehead sweetly.

When he finally spoke, he seemed concerned, but no less warm or sated. “How do you feel?”

“—Alright. Wonderful. Maybe sore.”

“You’re beautiful you know.” Roy said, the same swirl of too many thoughts returning to his expression again, covering his face and clouding his eyes with something unspoken and unreadable. Riza didn’t take her stock in beauty, but the compliment ran deeper than that and she exhaled, the ache moving to her chest. There was something else he couldn’t tell her, and she couldn’t bear to ask.

Instead, she smiled. “I’m glad we did that.” 

“Me too.” He replied, purring against her side before he propped himself up to kiss her. “Tired, though.”

“Mmmhm.” Riza rumbled in agreement, tucking herself into his arms as she moved to pull a blanket over them both. “Sleep sounds nice.”

“It does.” Silence lulled them into a state of peacefulness, and Roy only broke it to offhandedly murmur, “-sounds like it’s raining outside.”

Straining, Riza heard the summer thunder. “It is.” She said softly.

“I never really liked the rain. I always thought it was too sad. Melancholy, almost.”

 In Riza’s mind, it had already been filed away as the sound of a fresh memory, something gone but no less enjoyed. But Roy seemed to associate it with something else; something deeper and more bothersome. She kissed him gently, wanting to once more relieve the frown that he often slipped into.

“We can just sleep through it.” Massaging the back of his neck, she felt him melt against her touch, leaning into her as he wrapped an arm over her, a movement that was almost habitual now, but not quite.  

“I like that idea.” He said, and Riza nodded sleepily, tucking herself under his chin as sleep wore into her, and a new calmness swept through her veins. Roy mouthed something into her hair that was inaudible, and then the dreams washed away everything but the feeling of his arms around her.

**Notes for the Chapter:**

> Merry Christmas and Happy Holidays everybody! The final chapter will be posted next Monday. All your kudos and reviews are wonderful, so thank you very much for following along. If you haven't seen it already, tumblr artist/friend Luckeh illustrated a scene from [Chapter 3](http://missturdle.tumblr.com/post/37752558745/pugletto-a-few-minutes-passed-of-them-simply>Chapter%203</a>%20for%20me.%20I%20hope%20the%20holiday%20season%20is%20going%20splendidly%20for%20you%20all!).


	6. Chapter 6

**Notes for the Chapter:**

> Late August, 1903. Ashford, Eastern Amestris.

The next morning, Roy had coaxed Riza into the shower with him, standing them both under the warm spray of water as he slipped his hands over her hips. The heat eased the dull ache in her body, and Riza had smiled as Roy’s hair plastered to his skin, and rivulets of water washed down his chest. When he ducked his head to grab the soap, water hit her face, and she laughed in surprise, taking them both down in a fit of soapy laughter. They hugged, Riza leaning into his shoulder thoughtfully before Roy finally sighed and turned off the water. 

“Consider that your send off.” She had said, stepping out onto the bathroom rug, stealing his towel. Roy followed, biting his tongue as he took the remaining towel and brushed his hair back from his eyes.

 “I’ll take that with me, and remember it fondly.” He’d said playfully, before she leaned up for one last kiss. 

 Getting dressed had happened alone, Riza stretching her arms and legs until she felt loose and limber again. Her toes had curled into her carpets as she slipped on clothes, pulling on a light blouse and shimmying into a dark blue skirt that reminded her of Amestrian uniforms in color. By the time her father had arrived home, her hair had dried, and any evidence to anything out of the ordinary had been locked away within her. Muscle memory kept Roy under her skin, invisible to anyone but herself. Even her clothes spoke to nothing unusual, and Riza braced herself for the storm that had yet to hit.

 Avoiding Roy’s official announcement of his departure for the Military Academy wasn’t as easy as it had initially sounded. From her place down the hall, she could still hear the even and soothing convictions of Roy’s voice against the increasingly upset timbre of her father’s. While she had already expected the outcome, the severity of her father’s voice as he told Roy to get out of the house still reeled her with shock and a sudden bitter taste in her mouth. It was final. But then, it already had been a final decision in Roy’s mind. It just seemed too soon. 

He was packed. And though she avoided going to him as he marched out of her father’s study, she heard him call the taxi all the same, knew in the knot of her stomach that leaving meant _now_ , not tomorrow and not at the end of the week. 

It took less than an hour for him to pull his trunk and suitcase down the stairs and to the manor’s front porch. When Riza saw the small black cab rolling down the far end of the street from her bedroom window, she rushed down the back staircase quickly, avoiding her father’s ire to push open the front door, and catch one last glance of Roy Mustang. He startled when she exhaled in relief at having made it in time, and Roy turned, his black coat moving over his shoulders as he looked back at her. It was clear that she wanted to kiss him, and he hesitated, as if hoping that if he’d step closer, they would finish the action together, but neither of them moved as the car rolled to the front of the house.

“These are yours.” Roy said quietly, handing the folded pages of their notes over to her. “I was hoping to give them back, so you could figure out what you wanted to do with them.” 

Taking them into her hands, Riza marveled at the clever addition of a green ribbon to wrap the bundle. For a soldier, of course. Not traditional letters home in any sort of sense, but she could keep it in her desk and consider the women who chose to wear ribbons in their hair again. Perhaps they couldn’t be blamed for that small connection after all; though Riza was still convinced what she had taken was far more of a tether to him than a simple bow. If nothing else, she trusted him - and he trusted her. 

That alone could move her forwards without regret. 

“Thank you.” Riza said quietly, looking at the cab driver who had stopped before she glanced back at roy. “Good luck, I suppose.” 

Roy nodded, reaching for his luggage. “Thank you. For that. For everything.”

“I had better see you again, Mister Mustang. Maybe when you’ve graduated.” Something hot pricked at Riza’s eyes, but she blinked it away and smiled back at him.

“That’s a promise.” Roy said with a casual but forced grin. He hesitated, palming her shoulder for a moment before he withdrew his hand and sadness flickered over his gaze for a moment. “When you least expect me.” 

“You’re only saying that because you plan to show up unexpected.”

“Maybe.” Roy laughed. “Goodbye, Miss Hawkeye. I’ll think about you.” 

“You should focus on your studies.” She said firmly. “Goodbye.” 

Roy laughed, something that was laced with a kind of pain Riza hadn’t expected and wanted to take back, but his eyes were bright and she thought better of saying anything more. This was a moment of happiness for him, even if he was loathe to admit it - a purpose was what got Roy up in the morning. Instead, she gave him a slight nod in response, and watched as he loaded his things into the car and slipped into the passenger’s seat, waving as the automobile pulled away and out of sight, leaving Riza standing alone on the front step of her porch. 

When the car vanished from her line of sight, Riza turned, slipping back inside the Hawkeye household. She ghosted her way past her father’s study, stopping only when he remarked to her from his seat at his desk, “That boy doesn’t understand what he’s thrown away. Good riddance.” Berthold Hawkeye’s lips twisted downward in disdain, underneath ragged bangs that spilled over his eyes, and guarded his face. The dust of his study swirled in the edge of light from the hall, keeping her father in a musty shadow. Coughing, Berthold returned to his notes, scrawling out complex formulas with dipped ink and an iron pen. 

Riza inhaled sharply, but said nothing, face schooled in a blank and perceptive expression.

“It’s just you and I again, little bird.” Berthold said soberly. Adjusting his worn cravat as he leaned further into his books, he hummed lowly, pushing aside papers. It was the sound of a Master falling into his work - the magnum opus that Roy had wanted to obtain, and Riza had spent years watching her father finish. “Later this week, I will show you what I’ve learned from my trip. I think this is a breakthrough for my manuscript, and I need your help.”

Riza nodded. “Of course, father. If you’ll excuse me, I need to finish my studies.” The last words trembled from her lips and she swallowed them back before fading away as her father grunted an affirmative. Berthold Hawkeye would return to his inkwell without a second thought, and it was clear that her father’s eyes were already more intent on his work than they were on her. For once, Riza felt a rush of gratitude for their shared silences, and her father’s slipping presence when confronted with his studies.

The wood creaked as she leaned away from the door frame and walked down the rest of the hall, stopping to stare at the shell that had been Roy’s room, empty and gutted. It was strange, and she forced her gaze away from the opened door to duck inside her own room. 

Locking the bedroom door behind herself, Riza collapsed into her bed, bundle of notes still in her hands. Fingers shaking as she loosened the ribbon, Riza let the pages spill across her bed, each filled with chemical equations, with notes, with words and phrases that Roy had added or thought amusing. It had become more than the experiment, within she found other code keys, alchemy notes on the properties of several metals, a jotted note on the illegality of transmuting gold, and lines of poetry he had been attempting to memorize. 

On the last page, fresh blue ink had been printed neatly, and Riza laid it down before her, blinking back a blur that threatened to break her ability to read it:

 

  _‘The amount of energy required to break a covalent bond is equal to the amount of energy released when the bond is made, and that value is known as the bond energy.’_

 Turning away from his words, she pulled a pillow to her face, and for the first time in a long time, Riza cried.

**Notes for the Chapter:**

> Well, Happy New Year's everyone! I have to say, I'm genuinely excited to say this is the final chapter of The Concupiscence Conjectures. This story ends here; and I'll admit, I am quite nervous about the ending, moreso than anything else, I had to have it feel "right". This is what I came up with, and I hope you agree with me. For those curious, and to clear it up: Roy's alchemy code was "Molybdenum, Boric Trioxide, di-Hydrogen, Chlorine, Cobalt, Silicon." [all body parts] and " K, H2, Cu, Li, Fe, S, Bi" all actions/doing verbs. It's ah, not particularly a difficult code to figure out if you've got a bit of a dirty mind and some free time on your hands. The final notes that mention metallic properties are also important and give us a good insight into Roy's mind/what he's not quite saying to Riza. The bits of poetry are Roy's attempts to seem romantic and to memorize more lines and codes and meters; it's not simply a matter of him trying to impress her, he's actually trying to improve his references breadth. Lastly, Roy returned the notes to Riza because they were not meant for him and he has absolutely no intention of making comparative notes on women. The idea bothers him a great deal, and it was more about Riza. It wouldn't sit right with him to keep _her_ experiences on hand. 
> 
> I hope you all enjoyed this very much, and I'm pleased to say that there will be a sequel, starting next Sunday! Please keep an eye out for _**The Logogriph Letters**_.

**Author's Note:**

> The summer of 1903 places Riza at the age of sixteen and Roy at the age of eighteen, for those who wondered.


End file.
